Vaccine recommendations focus of ACIP’s October meeting
CDC’s Advisory Committee on Immunization Practice (ACIP) met in Atlanta on October 29–30, 2014, to discuss and update vaccine recommendations. Following is a summary of select committee discussions.
The committee presented an update on the effectiveness of the live attenuated influenza vaccine (LAIV; FluMist—MedImmune) and the injectable vaccines over the last three influenza seasons among individuals aged 2 years to 18 years. The type of circulating virus changed every year.
For LAIV, effectiveness against medically attended influenza was 60%, 46%, and 0% during the 2011–12, 2012–13, and 2013–14 seasons, respectively. Note that the numbers enrolled in this study were small for the 2- to 8-year-old cohort. Inactivated influenza vaccine (IIV) effectiveness was 61%, 47%, and 60%, respectively. Therefore, the relative effectiveness favored the IIV for the 2013–14 season, with no difference during the 2012–13 season. Since the A(H1N1) virus was predominant in the 2013–14 season, perhaps LAIV was not effective against this virus.
Asked to respond to the findings, MedImmune found similar results but observed some differences by vaccine lot that may be explained by potency loss of the A(H1N1) strain resulting from temperature control issues. Another MedImmune study found that early shipments of the vaccine showed loss of effectiveness and higher effectiveness later in the season.
A U.S. Department of Defense study also found low to negative vaccine effectiveness for LAIV in this last season. This is incongruent with ACIP’s decision in June 2014 to preferentially recommend LAIV for children aged 2 to 8 years on the basis of earlier studies. The committee hopes that surveillance during this current season will help determine the cause of these findings.
Currently, only 15% of adults have received tetanus–diphtheria–acellular–pertussis (Tdap). During the June 2013 meeting, ACIP decided not to recommend routine revaccination with Tdap, except for select populations. This decision was based on data showing modest efficacy (75%) during the first year and rapidly waning titers. At that time, the recommendation for vaccination of pregnant women during every pregnancy was made. ACIP also decided to look into revaccination of select populations, one of which is health care providers.
The pertussis working group concluded that while pertussis transmission in hospitals does occur, the risk to health professionals is unclear because of lack of studies. Because there is no evidence that additional doses would be beneficial in preventing disease in the health care setting, the working group did not recommend a change in the current recommendations.
Human papillomavirus (HPV)
New data were presented on the 9-valent human papillomavirus vaccine (HPV9) that was submitted to FDA in December 2013. This vaccine covers 90% of the high-risk HPV types that cause cancer in humans. The 9-valent vaccine is manufactured the same way as the 4-valent vaccine (Gardasil—Merck), with the same adjuvant. Immunobridging studies (efficacy based on similar titers) was performed in adolescents and men and compared with studies in young women. The adverse effect profile is similar to the 4-valent vaccine (HPV4). Data demonstrated a decrease in gynecological procedures (biopsies and therapeutic procedures) in HPV9-vaccinated patients compared with HPV4-vaccinated patients.
Evaluating the cost effectiveness of changing to a 9-valent vaccine was modeled. Currently, the 4-valent program is cost effective, and changing to a 9-valent program is more cost effective and potentially cost saving. Most of the cost effectiveness is seen in girls, primarily due to a reduction in cases of cervical cancer. Impact depends on vaccine uptake and duration of protection, both of which are unpredictable. It is expected that one additional case of cervical cancer will be prevented for every 1,000 individuals vaccinated with HPV9 instead of HPV4.
A GRADE (Grading of Recommendations Assessment, Development, & Evaluation) analysis, a systematic approach to making a decision based on the quality of evidence and strength of recommendation, will be conducted and presented at the February ACIP meeting.
The HPV working group is also evaluating a two-dose versus a three-dose schedule for the HPV vaccine. Current vaccine coverage for girls is approximately 38% for the three-dose series. Results of immunogenicity studies comparing the two versus three doses were similar; however, effectiveness was slightly lower. In addition, the duration of protection as evaluated by antibody levels appeared to be shorter in the two-dose schedule compared with the three-dose schedule. Several countries around the world are using the two-dose schedules. There is also an ongoing trial using the 9-valent vaccine in a two-dose schedule.
The 9-valent vaccine is a three-dose schedule. It will probably be licensed for females aged 9 to 26 years and males aged 9 to 15 years. The working group will make policy suggestions after the vaccine is approved but does not expect to recommend revaccination of those already given HPV4 with HPV9.